Critical conditions of polymer film combustion in gaps

Abstract

In the case of combustion of polymer films, there is always a critical film thickness, such that at thicknesses smaller than this thickness, the flame is not propagated along the film. In this study, a determination is made of the critical thickness and the critical flame propagation velocity for polymer films on copper wires stretched along the axis of glass tubes of different diameters. Experiments were carried out on PMMA and nitrocellulose films. This made it possible to estimate to some degree the effect of the oxidizer present in the polymer molecule. At tube diameters greater than 15 mm, the critical thickness and critical flame propagation velocity are the same as for open combustion. For tube diameters smaller than 15 mm, the critical thickness begins to increase as the tube diameter decreases, slowly at first, then more rapidly. Likewise, the critical flame propagation velocity begins to fall rapidly with decrease in tube diameter.